U.S. Pat. No. 3,757,864, the teachings of which are specifically incorporated herein by reference, teaches that certain aluminum salts of orthophosphate esters can be employed to decrease the friction loss of and/or gel nonpolar organic liquids. It is often desirable to incorporate into gelled liquids a chemical which will effectively cause the viscosity of the liquid to decrease after a predetermined period of time. For example, in fracturing petroleum producting formations it is desirable to remove the fracturing fluid from the formation following the treatment to prevent a restriction on the flow of petroleum fluid therefrom. Gelled fluids can most often be more easily and effectively removed if the viscosity can be reduced after the formation is fractured. In other situations, for example, where solids are being transported through a pipeline as a suspension of such solids in a gelled fluid, it is desirable to reduce the viscosity of the fluid when the solids are to be removed from the liquid.
The present invention concerns the discovery of a group of chemicals which can be employed to break (cause at least a 75 per cent reduction in the maximum viscosity of the liquid) an essentially nonpolar organic liquid which is gelled with an aluminum salt of an orthophosphate ester in the manner taught in U.S. Pat. No. 3,757,864. Acids, e.g. acetic acid, hydrochloric acid and bases, e.g. amines as taught in U.S. Pat. No. 3,505,374, break these types of gels. However, the break occurs immediately which is undesirable in fracturing operations.